Function based continuous exhaust valve control

ABSTRACT

A system for controlling exhaust noise in a vehicle includes a variable exhaust valve for an exhaust system, and an exhaust valve controller operatively connectable to the variable exhaust valve. The exhaust valve controller is configured to retrieve two or more control conditions, and determine an operational intent based on the two or more control conditions. The exhaust valve controller is configured to generate a control signal based on the operational intent and the two or more control conditions, and transmit the control signal to the variable exhaust valve. The control signal changes an exhaust valve position of the variable exhaust valve. The exhaust valve position is configured to create an exhaust noise response associated with the operational intent.

INTRODUCTION

The subject disclosure relates to exhaust valve controls, and more specifically, to a function-based continuous exhaust valve control.

Vehicle exhaust systems can experience peak volumes of engine noise during certain events like startup, acceleration, and gear changes. To control the exhaust noise some exhaust systems include one or more bi-state exhaust valves installed in-line with the exhaust system(s). A bi-state exhaust valve has two settings: open and closed, which can either restrict flow of exhaust gases (and reduce exhaust noise) or allow the gases to pass without restricting the noise. When the valve opens or closes, the noise levels can drastically change due to valve position discontinuities, which in some cases is an undesired effect. In addition a boom event is a region of increased noise caused by the presence of an acoustic mode in the exhaust system. These modes typically manifest as an increase and decrease in noise level as prominent orders pass through them as the engine rpm increases.

An exhaust control system is used to control the open or closed state of the valve based on control inputs that include, among other settings, gear state and engine revolutions per minute (rpm) of the vehicle. The control system may use a lookup table to match various combinations of the control inputs to an open or closed exhaust valve. Configuring bi-state control systems to include multiple valve settings can be impractical because of the many factors that must be considered to mitigate exhaust boom. For example, a vehicle with a ten speed transmission could have 7 rpm ranges and 13 gear states equaling 91 total values to set per performance mode. In bi-state valve systems, the controller uses a look-up table to match valve settings with the control factors according to an expected exhaust response. Providing partially-open valve positions in a bi-state valve system to accommodate multiple vehicle control factors like gear state, engine RPM range, pedal position, and performance mode of the vehicle could require calibration of a lookup table having thousands of variables.

Accordingly, it is desirable to provide a function-based continuous exhaust valve control that provides an infinitely-variable valve position using a limited number of control parameters. It may also be advantageous to provide a system that can automatically adjust valve positions based on user-selectable modes and controller-selected configurations based on various control parameters. It is also desirable to provide a continuous exhaust valve control that adjusts the exhaust valve angle in real-time using multivariate control functions that can be positioned according to control parameters detected by the controller.

SUMMARY

In one exemplary embodiment, a system for controlling exhaust noise in a vehicle includes a variable exhaust valve for an exhaust system, and an exhaust valve controller operatively connectable to the variable exhaust valve. The exhaust valve controller is configured to retrieve two or more control conditions, and determine an operational intent based on the two or more control conditions. The system is configured to generate a control signal based on the operational intent and the two or more control conditions. The controller is further configured to transmit the control signal to the variable exhaust valve. The control signal changes an exhaust valve position of the variable exhaust valve. The exhaust valve position is configured to create an exhaust noise response associated with the operational intent.

In another exemplary embodiment, a computer-implemented method for controlling exhaust noise in a vehicle is described. The method includes retrieving, via a processor, two or more control conditions. The method further includes determining, via the processor, an operational intent based on the two or more control conditions, and generating, via the processor, a control signal based on the operational intent and the two or more control conditions. The method includes generating, via the processor, a control signal based on the operational intent and the two or more control conditions. The method further includes transmitting the control signal, via the processor, to a variable exhaust valve that changes an exhaust valve position of the variable exhaust valve. The exhaust valve position is configured to create an exhaust noise response associated with the operational intent.

In addition to one or more of the features described herein, the exhaust valve controller is further configured to determine an operational intent based on the two or more control conditions. The operational intent is associated with a particular exhaust valve position. The exhaust valve controller is further configured to determine the control signal based on a sigmoid function and the operational intent.

According to another embodiment, the operational intent is user-selectable by a user of the vehicle.

According to yet another embodiment, the operational intent includes a first mode configured for a higher decibel exhaust noise, and a second mode configured for lower decibel exhaust noise.

According to another embodiment, the control signal comprises a dynamic rate setting indicative of a predetermined rate of change for the variable exhaust valve. The dynamic rate setting is based on the operational intent.

According to another embodiment, the controller is configured to determine the operational intent based on the two or more control conditions according to a continuous sigmoidal function.

According to yet another embodiment, the operational intent is cruising, and the controller is configured to retrieve a rate of change of engine torque, retrieve a vehicle acceleration, and position the variable exhaust valve based on the rate of change of engine torque and the vehicle acceleration.

In yet another embodiment, the operational intent is quasi-static, and the controller is configured to retrieve an engine torque, retrieve a rate of change of engine torque, and position the variable exhaust valve to mitigate valve dither based on the engine torque and the rate of change of engine torque.

According to another embodiment, the operational intent is pedal flare, and the controller is configured to, retrieve an engine torque, retrieve a rate of change of engine torque, and position the variable exhaust valve based on the engine torque and the rate of change of engine torque, and the position is configured to produce a higher decibel exhaust noise.

In another embodiment, the operational intent includes a start type. The start type includes a keyed start and an auto start. Responsive to a vehicle startup, the controller is configured to position the variable exhaust valve based on the start type.

In another embodiment, the method includes determining, via the processor, an operational intent based on the two or more control conditions wherein the operational intent is associated with a particular exhaust valve position, and generating, via the processor, the control signal based on a sigmoid function and the operational intent.

According to one exemplary embodiment, the operational intent is user-selectable by a user of the vehicle.

In another exemplary embodiment, the operational intent includes a first mode configured for a higher decibel exhaust noise, and a second mode configured for lower decibel exhaust noise.

In another embodiment, the method includes transmitting the control signal by transmitting the control signal to a variable exhaust valve, and changing, via the control signal, an exhaust valve position of the variable exhaust valve. The control signal includes a dynamic rate setting indicative of a predetermined rate of change for the variable exhaust valve. The dynamic rate setting is based on the operational intent.

In another embodiment, the method includes evaluating, via the processor, the operational intent based on the two or more control conditions according to a continuous Sigmoidal function.

In another embodiment, the method includes determining, via the processor, that the operational intent is cruising, retrieving a rate of change of engine torque via the processor, retrieving a vehicle acceleration via the processor, and positioning the variable exhaust valve, via the processor, based on the rate of change of engine torque and the vehicle acceleration.

In yet another exemplary embodiment, the method further includes determining, via the processor, that the operational intent is quasi-static, retrieving an engine torque via the processor, retrieving a rate of change of engine torque via the processor, and positioning the variable exhaust valve, via the processor, to mitigate valve dither based on the engine torque and the rate of change of engine torque.

According to yet another exemplary embodiment, the computer-implemented method further includes determining, via the processor, that the operational intent is pedal flare, retrieving an engine torque via the processor, retrieving a rate of change of engine torque via the processor, and positioning the variable exhaust valve, via the processor, based on the engine torque and the rate of change of engine torque. The position is configured to produce a higher decibel exhaust noise.

In yet another embodiment, the method includes positioning, via the processor, the variable exhaust valve responsive to a vehicle startup. The positioning is based on a start type comprising a keyed start and an auto start.

The above features and advantages, and other features and advantages of the disclosure are readily apparent from the following detailed description when taken in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

Other features, advantages and details appear, by way of example only, in the following detailed description, the detailed description referring to the drawings in which:

FIG. 1 depicts an exemplary vehicle according to an exemplary embodiment;

FIG. 2 is a diagram of a system for controlling exhaust noise in the vehicle of FIG. 1, according to an exemplary embodiment;

FIG. 3 is a top schematic view of a variable exhaust valve cylinder for use in the system of FIG. 2, according to an exemplary embodiment;

FIG. 4 is a flow chart of a method for controlling exhaust noise using the system of FIG. 2, according to an exemplary embodiment; and

FIG. 5 is a graph of a multivariate function for controlling exhaust noise with the system of FIG. 2, according to an exemplary embodiment.

DETAILED DESCRIPTION

The following description is merely exemplary in nature and is not intended to limit the present disclosure, its application or uses. It should be understood that throughout the drawings, corresponding reference numerals indicate like or corresponding parts and features. As used herein, the term module refers to processing circuitry that may include an application specific integrated circuit (ASIC), an electronic circuit, a processor (shared, dedicated, or group) and memory that executes one or more software or firmware programs, a combinational logic circuit, and/or other suitable components that provide the described functionality.

In accordance with an exemplary embodiment, FIG. 1 depicts a vehicle 100 having a system 102 for controlling exhaust noise. In some aspects, the exhaust noise may be produced by an exhaust system 108 of vehicle 100. System 102 includes a variable exhaust valve 104 and an exhaust valve controller 106. Although a performance vehicle is shown, it should be appreciated that vehicle 100 can be any vehicle having a exhaust system for a combustion engine such as, for example, a car, truck, utility vehicle, etc.

FIG. 2 depicts the system 102 for controlling exhaust noise in vehicle 100, according to an exemplary embodiment. Referring now to FIG. 2, system 102 includes variable exhaust valve 104 installed inline with exhaust system 108. Variable exhaust valve 104 includes a valve actuator 206 coupled to a variable exhaust valve cylinder 204. Valve actuator 206 is configured to change the position of a valve mechanism 202 by rotating valve mechanism about an axis perpendicular to the direction of gas flow through exhaust system 108. Variable exhaust valve 104 can be operatively connected to exhaust valve controller 106 via a control bus 208. Although variable exhaust valve 104 changes position of valve mechanism 202 by rotating about an axis perpendicular to the direction of gas flow, it is appreciated that valve mechanism 202 may open and close in other ways. In some aspects, variable exhaust valve cylinder 204 may take other shapes to accommodate various mechanisms for opening and closing the valve. For example, exhaust system 108 may include square or rectangular exhaust pipes, and variable exhaust valve cylinder 204 may be a similar shape. Variable exhaust valve 104 may be configured to open and close in other multi-variable configurations.

Exhaust valve controller 106 is a control module that can include one or more processors 110 operatively connected to computer memory (not shown) of exhaust valve controller 106. Processor 110 is configured to process the inputs from one or more engine sensors (not shown) or vehicle computers (not shown) in real-time. Exhaust valve controller 106 may contain both hardware and software (firmware, computer programs, calibration data, etc.). Exhaust valve controller 106 may be operatively connected to and in communication with one or more vehicle computers such as the vehicle electronic control module (ECM) (not shown), and/or one or more sensors (not shown) that are configured to retrieve vehicle control conditions.

Exhaust valve controller 106 can be operatively connected to a user interface 210. User interface 210 may be a hard control (e.g., a knob, a button, a selectable switch, etc.) or may be a soft control (e.g., a user-selectable option in a digital interface, touch screen, etc.). User interface 210 may be configured to receive one or more user inputs that indicate a desired exhaust sound characteristic of vehicle 100. The sound characteristic may be user-selectable based on the operational intent of vehicle 100. For example, user interface 210 may include one or more settings indicative of operational intent such as highway, cruising, racing, performance, etc. Each respective operational intent includes a predetermined sound profile associated with it. For example, if an operational intent is “performance,” the sound profile associated with performance may include full-bodied, high-decibel exhaust sounds that allow the full character of the engine to reverberate throughout the exhaust system. In another aspect, an operational intent may be “cruising,” which may be associated with low-decibel exhaust sounds.

According to some embodiments, exhaust valve controller 106 may receive the user input from user interface 210, and determine an operational intent based on the input. Exhaust valve controller 106 may determine operational intent based on the user interface input alone, or may determine the operational input based on the user input in conjunction with other performance factors (e.g., control conditions) of vehicle 100. The other factors may be, for example, vehicle speed, engine rpm, engine torque, rate of change of rpm, and rate of change of engine torque, among others.

Variable exhaust valve 104 may be configured to receive control signals from exhaust valve controller 106, and create a particular exhaust noise response appropriate for (associated with) with a particular operational intent. An exhaust noise response may be, for example, a predetermined amplitude of sound (in decibels) output by exhaust system 108. The sound characteristic (amplitude of sound) is associated with the operational intent. For example, if vehicle is operating in a quiet neighborhood early in the morning, it may not be desirable to produce the same sound as when the vehicle is operating in performance mode or in a racing environment. Exhaust valve controller 106 may retrieve control conditions (that may include user input from user interface 210), and determine the operational intent based on the control conditions. Processor 110 may generate a control signal based on the operational intent, and transmit the control signal to valve actuator 206. Valve actuator 206 can be configured to receive the control signal and change the position of valve mechanism 202 based on the instructions received from exhaust valve controller 106.

FIG. 3 is a top view of a variable exhaust valve cylinder 204 for use in the system of FIG. 2, according to an exemplary embodiment. As depicted in FIG. 3, variable exhaust valve cylinder 204 may be configured inline with the direction of exhaust gases through exhaust system 108. Variable exhaust valve 104 may change the position of the valve mechanism 202 by rotating valve mechanism 202 via valve actuator 206 (not shown in FIG. 3 for clarity) to a particular angle 302 with respect to a centerline 304 of variable exhaust valve cylinder 204. As explained above, valve mechanism 202 may take a different shape that that shown herein, and may be actuated in a different way.

Each position of valve mechanism 202 can be configured to create a particular exhaust noise response. For example, a valve mechanism in a fully closed position (e.g., position 202A) may produce a lower decibel noise response than a partially open position (e.g., position 202B). A partially open position (e.g., position 202C) may produce a higher decibel noise response than the more closed positions (e.g., position 202B). Although only three positions are shown in FIG. 3, it is appreciated that system 102 can be configured to adjust variable exhaust valve 104 to an infinite number of positions that can produce any number of pre-defined exhaust noise responses.

In some aspects, exhaust valve controller 106 may determine a rate at which valve actuator 206 changes the angle of valve mechanism 202. The rate of change is changed dynamically, based on various control factors in real-time in addition to predetermined rates associated with operational intent, therefore it is considered a dynamic rate setting. By modifying the rate of change for changing the exhaust valve position, exhaust valve controller 106 can mitigate unwanted sudden changes in noise levels associated with a sudden opening of variable exhaust valve 104 from a closed or partially closed position. In some aspects, exhaust valve controller 106 may determine a dynamic rate setting based on the determined operational intent.

FIG. 4 depicts a flow chart of a method 400 for controlling exhaust noise using the system of FIG. 2, according to an exemplary embodiment. Referring now to FIG. 4, block 402 depicts a step in which processor 110 is configured to retrieve two or more control conditions. In some aspects, processor 110 may retrieve control conditions from an operatively connected vehicle computer, and/or one or more auxiliary sensors configured to determine the control conditions. Control conditions can include, for example, a vehicle velocity, a vehicle rate of change of velocity (vehicle acceleration), engine torque, a rate of change of engine torque, engine rpm, gas pedal position, a rate of change of the gas pedal position, a time factor (e.g., a length of time at which a control factor remains unchanged), a predetermined threshold that includes a value at which processor 110 triggers transmission of one or more control signals that start or stop continuous function-based valve control. Other control factors are contemplated.

At block 404, processor 110 may determine an operational intent based on the two or more control conditions. The operational intent is associated with a particular exhaust valve position. In some aspects, the operational intent is user-selectable by a user of vehicle 100. Accordingly, exhaust valve controller 106 may retrieve information from user interface 210 indicative of an operational intent. The operational intent may include pre-defined sound profiles or modes that control how the exhaust system sounds. For example, operational intent could include a first mode configured for a higher decibel exhaust noise (e.g., for racing and/or performance, intentionally revving the motor with a pedal flare, etc.) and a second mode configured for lower decibel exhaust noise (e.g., cruising mode, etc.).

In other aspects, the operational intent is automatically determined by the processor based on two or more control conditions. For example, in one embodiment, processor 110 may determine that vehicle 100 is in cruise condition based on an observed vehicle speed over a predetermined period of time. Processor 110 may further determine the operational intent based on a gas pedal rate of change indicative of how quickly the driver has pressed the gas. The pedal rate of change is tied to engine torque rate of change. Even if a user-selected operational intent is set to the first mode (performance), which may generate a higher decibel noise profile, processor 110 may generate a control signal configured to quiet the car to avoid uncomfortable continuous noise.

As represented by block 406, processor 110 may generate the control signal based on the operational intent and the two or more control conditions. In some aspects, processor 110 may be configured to generate the control signal based on the two or more control conditions according to a continuous sigmoidal function. Processor 110 may retrieve two or more control conditions (e.g., engine rpm and engine torque) and apply the control conditions to the sigmoid function as inputs. In some aspects, processor 110 may further generate the control signal based on a multivariate function that includes a Gaussian function.

If the control signal is envisioned as a graph, the sigmoid function is chosen to produce the basic shape of the sigmoid graph. According to some embodiments, exhaust valve controller 106 may set the basic response function based on engine rpm and torque with a sigmoid function. There is a natural preference to close the valve at low speed and torque and open it at high rpm and torque, with a saturation point (valve completely open) occurring somewhere before max rpm and max torque. The Sigmoid function naturally follows this response.

Referring briefly to FIG. 5, a graph of a base sigmoid function with a Gaussian function added for controlling exhaust noise is depicted according to an exemplary embodiment. A sigmoid function is a mathematical function having an “S” shaped curve (sigmoid curve). As depicted in FIG. 5, one embodiment of the exhaust valve controller 106 can be configured to determine valve opening as a function of control factors that include engine rpm and a sigmoid bias. In some aspects, processor 110 controls the sigmoid function surface using only four parameters, two bias terms and two weight terms. Two sigmoid bias terms are defined: one for the RPM axis and one for the torque axis. The bias parameters is directly related to engine rpm and torque at which motion of variable exhaust valve 104 occurs (as a translation in rpm and torque). Two weight terms are also defined: one for the rpm axis and one for the torque axis. The weight “W” is the slope of the control surface, which determines how quickly the valve opens/closes as the rpm and torque change. For example, one exemplary embodiment defines valve opening as a function of RPM such that

valve opening (as a percentage)=1/(1+e ^(−(Bias+W*rpm))).

As explained thus far, processor 110 may apply control factors as inputs to a sigmoid function to create the basic shape of the valve response control signal. According to one exemplary embodiment, a Gaussian function is used in conjunction with the sigmoid function to blend in and out of noise control regions (i.e., boom events etc.) based on the vehicle operating conditions. In mathematics, a Gaussian function, often simply referred to as a Gaussian, is a function of the form:

${f(x)} = {a\; e^{- \frac{{({x - b})}^{2}}{2a^{2}}}}$

for arbitrary real constants a, b and c. In some embodiments, real constants a, b, and c are associated with the two or more control conditions.

In the graph depicted in FIG. 5, valve angle (depicted in the Z-axis 502) is modeled as a function of engine RPM (shown as the X-axis 504) and pedal depression percentage (shown as the Y-axis 506). The Gaussian function provides the valley shaped features 508 in the graph of FIG. 5 that run the length of the rpm or y-axis. This function allows the control surface to deviate from the base sigmoid function and therefore eliminate boom events. The Gaussian function is used to blend in and out of noise control regions (i.e., boom events) based on the vehicle operating conditions. A Gaussian function is chosen to mitigate the boom events caused by the presence of an acoustic mode in the exhaust system because it matches the shape of the typical response in both rpm and torque. These modes typically manifest as an increase and decrease in noise level as prominent orders pass through them as the engine rpm increases, and have a shape similar to a Gaussian function with a height and width.

The Gaussian function defines the intended control surface, or in other words the intended position of the valve based on pedal percentage (position) and engine rpm. If the pedal or the engine rpm changes very quickly the valve would also move very quickly, which could result in a sudden change in noise. In one embodiment, exhaust valve controller 106 may generate the control signal based on the control conditions and the operational intent using the sigmoidal function to establish a base motion of the valve, and the Gaussian function to mitigate exhaust system boom by deviating from the base function.

In another aspect, exhaust valve controller 106 may generate the control signal based on the control conditions that include a dynamic rate limiter. The Dynamic Rate limiter may be used to limit how quickly the valve can move. For example, if the pedal position changes quickly (e.g., a very forceful pedal push) then the intended control surface would command a sudden change in the valve angle, but the valve rate limiter would limit how quickly the valve could move. In this case the valve position would lag the commanded position to some degree but would also smooth the transition.

Referring again to FIG. 4, after generating the control signal, as represented in block 406, processor 110 may transmit the control signal to variable exhaust valve 104 as represented at block 408. The control signal is configured to change a position of variable exhaust valve 104. The exhaust valve position is configured to create an exhaust noise response associated with the operational intent.

In some aspects, the operational intent is user selectable, and may include predetermined settings for valve position. In other aspects, exhaust valve controller 106 determines operational intent based on various control factors in addition to the predetermined settings. For example, according to one embodiment, the operational intent is cruising, and processor 110 is configured to retrieve a rate of change of engine torque, retrieve a vehicle acceleration, and position the variable exhaust valve 104 based on the rate of change of engine torque and the vehicle acceleration. As described above, processor 110 may determine that vehicle 100 is in cruise condition based on an observed vehicle speed over a predetermined period of time.

Processor 110 may further determine the operational intent based on a gas pedal rate of change indicative of how quickly the driver has pressed the gas. The pedal rate of change is tied to engine torque rate of change. Even if a user-selected operational intent is set to the first mode (performance), which may generate a higher decibel noise profile, processor 110 may generate a control signal configured to quiet the car to avoid uncomfortable continuous noise.

In some aspects, exhaust valve controller 106 may determine whether an operational intent is “exit cruise mitigation.” Exhaust valve controller 106 may monitor a rate of change of pedal depression and/or monitor vehicle acceleration. The rate of change of velocity can indicate an operational intent requiring full power. Accordingly, exhaust valve controller 106 may exit the function and open variable exhaust valve 104.

According to another embodiment, exhaust valve controller may determine, based on a total amount of pedal depression, that an operational intent is to maintain the current state of operation. Stated in other terms, exhaust valve controller 106 may determine that the operational intent is quasi-static. A quasi-static operational intent indicates that, based on a predetermined threshold indicative of a change of pedal position (±2% or less, for example), minor changes can be ignored to prevent flutter (rapid and/or repeated changing of position of valve mechanism 202 by minute amounts) by variable exhaust valve 104. Although 2% is used as an example, it is appreciated that another threshold value may be used to determine operational intent.

A respective amount of gas pedal depression can affect engine torque. In particular, when the pedal is pressed a small amount, engine torque is increased in a similar small amount. When the gas pedal is pressed heavily (changing pedal position significantly) engine torque is affected in response. Accordingly, in one embodiment, processor 110 is configured to retrieve an engine torque, retrieve a rate of change of engine torque, and position the variable exhaust valve 104 to mitigate valve dither based on the engine torque and the rate of change of engine torque. Processor 110 may determine pedal position in place of engine torque.

In other aspects, it may be advantageous to determine when a pedal depression is a pedal flare (e.g., revving the engine while not moving). In some operational scenarios it may be desirable to hear the full sound character of the engine. Accordingly, it may be desirable to limit any mitigation of exhaust noise that would stifle the noise. In other aspects, it may be desirable to enhance the sound character with a partial opening of variable exhaust valve 104. According to one embodiment, processor 110 may determine, based on the pedal depression and rate of change of pedal depression, that the operational intent is a pedal flare. Accordingly, processor 110 can be configured to retrieve an engine torque, retrieve a rate of change of engine torque, and position the variable exhaust valve based on the engine torque and the rate of change of engine torque. The position may be configured to produce a higher decibel exhaust noise. In other aspects, the position may be configured to produce a predetermined sound characteristic. Examples of a sound characteristic may be an engine rumble, a gurgling sound, etc.

According to yet another embodiment, the operational intent can include a start type indicative of how a vehicle is started. This may be useful for determining an operational intent because some ignition systems are configured to turn off at vehicle stops (e.g., traffic lights), and seamlessly restart when the brake pedal is released. It may be beneficial to reduce the sound of startup to be as inaudible as possible. In other aspects, when starting with a keyed startup, a different sound characteristic may be desirable. In one embodiment, the start type may be either a keyed start or an auto start. Responsive to detecting a vehicle startup, exhaust valve controller 106 may be configured to position variable exhaust valve 104 based on the start type.

Embodiments described herein may provide fine-resolution valve control while simplifying calibration time for a particular exhaust system. Some embodiments may also improve sound quality by eliminating sudden change in exhaust noise and minimizing or enhancing drive-away boom noise. Applying continuous multivariate functions like a sigmoidal function and a Gaussian function to control inputs can provide the benefit of continuous control of exhaust sound using a minimal number of input parameters. Moreover, the input parameters are easily interpreted by personnel tasked with calibrating and refining the control system for a particular vehicle response.

Continuous functions also provide infinite number of valve positions. A continuous function allows for control without discontinuous jumps in valve position. If a valve is used to mitigate boom events, as described previously, a control strategy that results in discrete valve positions (or discontinuities) would result in discontinuities in the noise signal at a time when it is most sensitive, resulting in a noticeable event. In contrast, a continuously controlled exhaust valve allows the effect to be smoothly blended in and out minimizing the ability for a listener to notice the event.

The finer resolution of valve control can improve user experience because unwanted noises may be mitigated, and desired natural sound characteristics of the engine can be selectively enabled, and automatically detected by the system control factors that indicate a particular operational scenario (e.g., neighborhood driving, performance driving, cruising, etc.). The control factors may be automatically monitored by the system and used to enhance user experience.

While the above disclosure has been described with reference to exemplary embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from its scope. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the disclosure without departing from the essential scope thereof. Therefore, it is intended that the disclosure not be limited to the particular embodiments disclosed, but will include all embodiments falling within the scope thereof. 

What is claimed is:
 1. A system for controlling exhaust noise in a vehicle comprising: a variable exhaust valve operatively connected to an exhaust system; and an exhaust valve controller operatively connectable to the variable exhaust valve, the exhaust valve controller configured to: retrieve two or more control conditions; and determine an operational intent based on the two or more control conditions; generate a control signal based on the operational intent and the two or more control conditions; and transmit the control signal to the variable exhaust valve, wherein the control signal changes an exhaust valve position of the variable exhaust valve, wherein the exhaust valve position is configured to create an exhaust noise response associated with the operational intent.
 2. The system of claim 1, wherein the exhaust valve controller is further configured to: determine an operational intent based on the two or more control conditions wherein the operational intent is associated with a particular exhaust valve position; and generate the control signal based on a Gaussian function, a sigmoidal function, and the operational intent.
 3. The system of claim 1, wherein the operational intent is user-selectable by a user of the vehicle.
 4. The system of claim 3, wherein the operational intent comprises a first mode configured for a higher decibel exhaust noise, and a second mode configured for lower decibel exhaust noise.
 5. The system of claim 4, wherein the control signal to the variable exhaust valve comprises a dynamic rate setting indicative of a predetermined rate of change for the variable exhaust valve; and wherein the dynamic rate setting is based on the operational intent.
 6. The system of claim 1, wherein the controller is configured to determine the operational intent based on the two or more control conditions according to a continuous Gaussian function and a continuous sigmoidal function.
 7. The system of claim 1, wherein the operational intent is cruising, and the controller is configured to: retrieve a rate of change of engine torque; retrieve a vehicle acceleration; and position the variable exhaust valve based on the rate of change of engine torque and the vehicle acceleration.
 8. The system of claim 1, wherein the operational intent is quasi-static, and the controller is configured to: retrieve an engine torque; retrieve a rate of change of engine torque; and position the variable exhaust valve to mitigate valve dither based on the engine torque and the rate of change of engine torque.
 9. The system of claim 1, wherein the operational intent is pedal flare, and the controller is configured to: retrieve an engine torque; retrieve a rate of change of engine torque; and position the variable exhaust valve based on the engine torque and the rate of change of engine torque, and the position is configured to produce a higher decibel exhaust noise.
 10. The system of claim 1, wherein the operational intent comprises a start type comprising a keyed start and an auto start, and responsive to a vehicle startup, the controller is configured to position the variable exhaust valve based on the start type.
 11. A computer-implemented method for controlling exhaust noise in a vehicle comprising: retrieving, via a processor, two or more control conditions; determining, via the processor, an operational intent based on the two or more control conditions; generating, via the processor, a control signal based on the operational intent and the two or more control conditions; and transmitting a control signal, via the processor, to the variable exhaust valve, wherein the control signal changes an exhaust valve position of the variable exhaust valve, wherein the exhaust valve position is configured to create an exhaust noise response associated with the operational intent.
 12. The computer-implemented method of claim 11, further comprising: determining, via the processor, an operational intent based on the two or more control conditions wherein the operational intent is associated with a particular exhaust valve position; and generating, via the processor, the control signal based on a Gaussian function, a sigmoidal function, and the operational intent.
 13. The computer-implemented method of claim 12, wherein the operational intent is user-selectable by a user of the vehicle.
 14. The computer-implemented method of claim 13, wherein the operational intent comprises a first mode configured for a higher decibel exhaust noise, and a second mode configured for lower decibel exhaust noise.
 15. The computer-implemented method of claim 14, wherein transmitting the control signal comprises: transmitting the control signal to a variable exhaust valve; and changing, via the control signal, an exhaust valve position of the variable exhaust valve; wherein the control signal comprises a dynamic rate setting indicative of a predetermined rate of change for the variable exhaust valve; and wherein the dynamic rate setting is based on the operational intent.
 16. The computer-implemented method of claim 11, further comprising: evaluating, via the processor, the operational intent based on the two or more control conditions according to a continuous Gaussian function and a continuous sigmoidal function.
 17. The computer-implemented method of claim 11, comprising: determining, via the processor, that the operational intent is cruising; retrieving a rate of change of engine torque via the processor; retrieving a vehicle acceleration via the processor; and positioning the variable exhaust valve, via the processor, based on the rate of change of engine torque and the vehicle acceleration.
 18. The computer-implemented method of claim 11, further comprising: determining, via the processor, that the operational intent is quasi-static; retrieving an engine torque via the processor; retrieving a rate of change of engine torque via the processor; and positioning the variable exhaust valve, via the processor, to mitigate valve dither based on the engine torque and the rate of change of engine torque.
 19. The computer-implemented method of claim 11, further comprising: determining, via the processor, that the operational intent is pedal flare; retrieving an engine torque via the processor; retrieving a rate of change of engine torque via the processor; and positioning the variable exhaust valve, via the processor, based on the engine torque and the rate of change of engine torque, wherein the position is configured to produce a higher decibel exhaust noise.
 20. The computer-implemented method of claim 11, further comprising: positioning, via the processor, the variable exhaust valve responsive to a vehicle startup, wherein the positioning is based on a start type comprising a keyed start and an auto start. 